KR102433461B1 - Electrode with two layer coating, method of use, and preparation thereof - Google Patents

Abstract

Systems and methods for making and using a two layer coated electrode are provided. The two layer coated electrode may include a substrate, a first coating layer and a second coating layer. The first coating layer may include a mixture of iridium oxide and tin oxide, and the second coating layer may include a mixture of iridium oxide and tantalum oxide. The electrode can be used, for example, in an electrolyzer.

Description

Electrode having a two-layer coating, its use and manufacturing method

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is filed under 35 U.S.C. U.S. Provisional Patent Application No. 62/066,431, filed October 21, 2014, entitled "Two Layer Electrode with Improved Durability," under § 119(e), the entire disclosure of which is incorporated herein by reference in its entirety for all purposes. incorporated herein by reference).

technical field

Aspects relate generally to electrode coatings and, more particularly, to two-layer electrode coatings, methods of making the same, and uses.

In some embodiments, an electrode is provided. The electrode comprises an electrically conductive substrate, a first coating covering at least a portion of a surface of the electrically conductive substrate comprising a mixture of iridium oxide and tin oxide, and at least a portion of the first coating comprising a mixture of iridium oxide and tantalum oxide a second coating covering the

In some aspects, the electrically conductive substrate comprises a valve metal. In some aspects, the valve metal is selected from the group consisting of titanium, zirconium, niobium and tantalum. In some aspects, the valve metal is titanium.

In some aspects, the first coating comprises from about 30% to about 85% by weight iridium oxide. In some aspects, the first coating comprises from about 45% to about 65% by weight iridium oxide. In some aspects, the second coating comprises from about 40% to about 75% by weight iridium oxide.

In some aspects, the second coating comprises from about 40% to about 75% by weight iridium oxide. In some aspects, the second coating comprises about 65 weight percent iridium oxide.

In some aspects, the molar ratio of iridium oxide in the first coating to iridium oxide in the second coating is selected from the group consisting of 1:2, 1:1, and 2:1. In some aspects, the molar ratio of iridium oxide in the first coating to iridium oxide in the second coating is 1:1. In some aspects, the electrode provides a normalized life that is about 175% longer than an electrode comprising a single layer coating of the composition of the second coating. In some aspects, the electrode provides a referenced lifetime that is about 110% longer than an electrode comprising a single layer coating comprised of the composition of the first coating.

In some aspects, the electrode is an anode.

In some embodiments, a method of manufacturing an electrode is provided. The method includes applying a first coating layer comprising iridium oxide and tin oxide to at least a portion of the surface of the electrically conductive substrate; and applying a second coating layer including iridium oxide and tantalum oxide to at least a portion of the first coating layer.

In some aspects, the method further includes preparing the electrically conductive substrate to remove contaminants and develop the surface prior to applying the first coating layer.

In some aspects, the method further comprises drying the first coating layer after applying the first coating layer.

In some aspects, the method further comprises drying the second coating layer after applying the second coating layer.

In some aspects, the molar ratio of iridium oxide in the first coating to iridium oxide in the second coating is between about 1:2 and 2:1.

In some embodiments, a method of manufacturing an electrochemical device is provided. The method comprises at least an electrically conductive substrate, a first coating covering at least a portion of the surface of the electrically conductive substrate comprising a mixture of iridium oxide and tin oxide, and a first coating comprising a mixture of iridium oxide and tantalum oxide. manufacturing an electrode comprising a second coating covering the portion, and installing the electrode in an electrolyzer.

In some embodiments, a system comprising an electrolyzer is provided. The system comprises at least an electrically conductive substrate, a first coating covering at least a portion of a surface of the electrically conductive substrate comprising a mixture of iridium oxide and tin oxide, and a first coating comprising a mixture of iridium oxide and tantalum oxide. a second coating covering the portion, and a power source for supplying an electric current to the electrode.

In some aspects, the electrode is immersed in the electrolyte.

Various aspects of at least one embodiment are described below with reference to the accompanying drawings, which are not intended to be drawn to scale. The drawings are included to provide illustration and a further understanding of various aspects and embodiments, and are incorporated in and constitute a part of this specification, but are not intended to be limiting of the present disclosure. Where a reference sign follows a technical feature in a drawing, the detailed description, or any claim, that reference sign is incorporated for the sole purpose of increasing the understanding of the drawing and description. In the drawings, each identical or nearly identical element illustrated in the various drawings is denoted by the same number. In the interest of clarity, not all elements may be represented in all drawings. In the drawing,
1A is a side view of an electrode according to one embodiment of the present disclosure;
1B is a perspective view of an electrode according to one embodiment of the present disclosure;
2 is a schematic diagram of an electrochemical device according to an embodiment of the present disclosure; and
3 is a plot of cell voltage versus days during testing of electrode coatings.

An electrode is a solid electrical conductor through which an electric current enters or exits through an electrolyzer or other medium. The electrode can be used in any electrochemical process that requires an electrical conductor. For example, electrodes can be used in electrogalvanizing, electroplating, electrotinplating, electroplating, electrowinning (eg, electrowinning of metals such as copper, nickel, and zinc), and other electrochemical processes. The electrode can be used in any halogen emission process, such as hypochlorite, chlorate and chlor alkali production, or chlor organic synthesis. Electrodes can also be used in electrolytic chlorination systems and processes. Electrolytic chlorination systems and processes can produce sodium hypochlorite through electrolysis of brine solutions. For example, the OSEC® B series on-site electrolytic chlorination system, available from Evoqua Water Technologies (Warrendale, PA), provides on-demand and on-site electrolytic chlorination systems. Sodium hypochlorite is produced through electrolysis.

The electrode can be used in an electrolyzer. An electrolytic cell is an electrochemical cell that can be used to force a chemical reaction in a desired direction, overcoming the positive free energy exhibiting an involuntary reaction. Electrolyzers convert electrical energy into chemical energy or produce chemical products through chemical reactions.

An electrode in an electrolyzer may be referred to as either an anode or a cathode depending on the direction of current through the cell. The anode is the electrode where electrons leave the cell and oxidation of ions within the cell occurs, and the cathode is the electrode where electrons enter the cell and reduction of ions within the cell occurs. Under these conditions, the direction of current through the cell is from the anode to the cathode. Each electrode can be either an anode or a cathode depending on the process and the direction of current through the cell.

The design of the electrolyzer and its electrodes may depend on one or more factors. One or more factors are, for example, construction and operating costs, desired product, electrical, chemical and transport properties, electrode material, shape and surface properties, pH of the system (eg, electrolyte pH), and temperature of the system (eg, , electrolyte temperature), competing unwanted reactions, and unwanted by-products.

Depending on the electrochemical process, one or more properties of the process, such as the current density in the electrolyzer, the pH of the system (e.g., electrolyte pH), or the temperature of the system (e.g., the electrolyte temperature), of the system and process Effectiveness, for example, the service life of the electrode may be affected. For example, exposure to one or more of high current density, low pH, or high temperature can lower the useful life of the electrode. In some embodiments, exposure to one or more of high current density, low pH, or high temperature can cause passivation of the electrode.

Passivation is the inhibition of the decomposition reaction caused by the formation of an undissolved film. A decomposition reaction is a process in which the original state of a solvent becomes a solute. Anode and/or cathode passivation may result in one or more of a loss of capacity, an increase in power costs, and a decrease in anode and/or cathode quality. When titanium is used as the substrate, anode passivation is the coating and growth of an insulating titanium dioxide layer on the substrate, which increases the potential at the anode and causes deactivation of the anode. In some embodiments, exposure to one or more of high current density, low pH, or high temperature can cause wear of the electrode. Abrasion of an electrode or “electrode wear” is the removal of material from an electrode. In some embodiments, exposure to one or more of high current density, low pH, or high temperature can cause both passivation and wear of the electrode.

As noted above, the electrolyzer may include an electrolyte. An electrolyte is a substance that produces an electrically conductive solution when dissolved in a polar solvent, such as water. The solution is electrically neutral. The dissolved electrolyte separates into positive and negative ions uniformly dispersed throughout the solute. When an electrical potential or voltage is applied to the electrolyte solution, positive ions are attracted to the electron-rich electrode and negative ions are attracted to the electron-poor electrode. The movement of anions and cations in opposite directions in solution leads to an electric current. Electrolytes can be called strong or weak depending on the dissociation of the solute. An electrolyte is strong when a high proportion of the solute, for example greater than 50%, dissociates to form free ions. If a high proportion of the solute, for example less than 50%, does not dissociate, the electrolyte is weak. In some embodiments, the electrolyte may be NaCl acidified with HCl. In another embodiment, the electrolyte may be a platinum salt.

In some embodiments, the electrode may be exposed to an electrolyte having a low pH. An electrolyte having a low pH may mean an electrolyte having an acidic pH, for example, a pH of less than 7. For example, the electrolyte may be a strong acid electrolyte. In some aspects, the strong acid electrolyte may be sulfuric acid.

In some embodiments, a low pH may refer to an electrolyte having a pH of less than about 3. In some embodiments, low pH may refer to an electrolyte having a pH of less than about 2. In some embodiments, a low pH may refer to an electrolyte having a pH of less than about 1. In some embodiments, a low pH may mean a pH of less than about 0.8. In some embodiments, a low pH may mean a pH of less than about 0.6. In some embodiments, a low pH may mean a pH of less than about 0.4. In some embodiments, a low pH may mean a pH of less than about 0.2.

In some embodiments, the electrode may be exposed to an electrolyte having a high temperature. The high temperature may be a temperature at which the cell voltage of the electrode decreases undesirably. The high temperature may be a temperature greater than about 50°C. In some embodiments, the high temperature is greater than about 55°C. In some embodiments, the high temperature is greater than about 60°C. In some embodiments, the high temperature is greater than about 65°C. In some embodiments, the high temperature is greater than about 70°C.

In some embodiments, the electrodes may be exposed to high current densities. Current density is a measure of the density of current. It is defined as a vector whose magnitude is the current per cross section, and can be measured, for example, in amperes per square meter (A/m 2 ). High current densities can have undesirable consequences. For example, high current densities can have undesirable consequences for one or more of coatings, electrodes, electrolysers, and electrochemical devices. The electrode has a finite amount of resistance, which causes it to dissipate power in the form of heat. The current density must be kept low enough to protect the electrode from passivation or wear.

In some embodiments, the high current density is a current density that results in at least one of passivation and wear of the electrode. In some embodiments, the high current density may be greater than about 0.5 kA/m 2 . For example, the high current density may be greater than about 1.0 kA/m 2 . High current densities may be greater than about 1.5 kA/m 2 . In some embodiments, the high current density may be greater than about 2.0 kA/m 2 . For example, the high current density may be greater than about 2.5 kA/m 2 . In some embodiments, the high current density may be greater than about 3.0 kA/m 2 . For example, the high current density may be greater than about 3.5 kA/m 2 . In some embodiments, the high current density may be greater than about 4.0 kA/m 2 . For example, the high current density may be greater than about 4.5 kA/m 2 . In some embodiments, the high current density may be about 5.0 kA/m 2 . In some embodiments, the high current density may be about 15 kA/m 2 or less.

Electrodes can be coated by two coating layers, a combination of which limits passivation and wear in certain electrochemical applications. A coating layer may mean one application or more than one application of a coating. Through the use of electrodes with two coatings, a synergistic effect can occur. The synergistic effect may provide optimal (eg, increased) performance of the electrode as compared to the sum of the performance of the electrode having the first coating and the performance of the electrode having the second coating. For example, the application may have one or more of the following characteristics: low pH, high electrolyte temperature, and high current density. The first coating layer may include a mixture of iridium oxide and tin oxide, and the second layer may include a mixture of iridium oxide and tantalum oxide. The first and second coating layers, in combination, exhibit high catalytic activity, stability, longer lifetime, better performance, less down time in operation due to less frequent electrode replacement, and cost effectiveness. In some embodiments, at least one of the solutions for applying the first coating layer and the second coating layer may further comprise a solvent. In some embodiments, the solution for the first coating layer may further comprise an alcohol. For example, the solution for the first coating layer may further comprise 2-propanol. In some embodiments, the solution for the second coating layer may further comprise an acid. For example, the solution for the second coating layer may further include hydrochloric acid.

The first coating layer may be directly applied to the electrode substrate, and the second coating layer may be applied directly to the first coating layer. The first coating layer and the second coating layer may reduce at least one of passivation and wear of the electrode. In some embodiments, the first coating layer may reduce passivation of the electrode. In some embodiments, the second coating layer can reduce wear of the electrode.

As used herein, "single coating layer electrode" means an electrode coated on at least one of its surfaces by a single coating comprising a mixture. The single coating may be a mixture that reduces at least one of passivation and wear of the electrode. In some embodiments, the single coating may be a mixture comprising iridium oxide and tin oxide. In some embodiments, the single coating may be a mixture consisting essentially of iridium oxide and tantalum tin oxide. In some embodiments, the single coating may be a mixture of iridium oxide and tin oxide. In some embodiments, a single coating may be a mixture comprising iridium oxide and tantalum oxide. In some embodiments, a single coating may be a mixture consisting essentially of iridium oxide and tantalum oxide. In some embodiments, the single coating may be a mixture of iridium oxide and tantalum oxide. The mixture provided as a coating may be in a solid solution, for example a solid state solution. In this solid solution, the mixture may be in a single homogeneous phase.

As used herein, a “two coating layer electrode” refers to at least partially applying, on at least one of its surfaces, a first coating comprising the mixture to provide a first coating layer, and a first coating to provide a second coating layer. It means an electrode coated by a second coating to be coated with. More than one application of the first coating may be performed to achieve the desired coating loading. More than one application of the second coating may be performed to achieve the desired coating loading. The two coatings may be a mixture that reduces at least one of passivation and wear of the electrode. In some embodiments, the first coating can reduce passivation of the electrode. In some embodiments, the second coating may reduce wear of the electrode. In some embodiments, the electrode substrate surface may be at least partially covered by a first coating comprising the mixture. The first coating may be a mixture comprising iridium oxide and tin oxide. In some embodiments, the first coating may be a mixture consisting essentially of iridium oxide and tin oxide. In some embodiments, the first coating can be a mixture of iridium oxide and tin oxide. The first coating may be at least partially covered by a second coating comprising the mixture. In some embodiments, the second coating can be a mixture comprising iridium oxide and tantalum oxide. In some embodiments, the second coating may be a mixture consisting essentially of iridium oxide and tantalum oxide. In some embodiments, the second coating can be a mixture consisting of iridium oxide and tantalum oxide.

In some embodiments, the two coating layer electrode comprises an electrically conductive substrate, a first coating covering at least a portion of the surface of the electrically conductive substrate, comprising a mixture of iridium oxide and tin oxide, and a mixture of iridium oxide and tantalum oxide , a second coating covering at least a portion of the first coating. In some embodiments, the two coating layer electrodes consist essentially of an electrically conductive substrate, a first coating covering at least a portion of the surface of the electrically conductive substrate comprising a mixture of iridium oxide and tin oxide, and a mixture of iridium oxide and tantalum oxide. and a second coating covering at least a portion of the first coating. In some embodiments, the two coating layer electrode comprises an electrically conductive substrate, a first coating covering at least a portion of the surface of the electrically conductive substrate, comprising a mixture of iridium oxide and tin oxide, and a mixture of iridium oxide and tantalum oxide , a second coating covering at least a portion of the first coating.

The electrode substrate may be any substrate having electrically conductive properties. The electrode substrate may be any substrate having sufficient mechanical strength to act as a support for the coating. The electrode substrate may be any substrate that has corrosion resistance when exposed to the internal environment of the electrolyzer. The electrode substrate may be a metal. In some embodiments, the electrode substrate may be a valve metal or an alloy thereof. The valve metal is any transition metal of groups IV and V of the periodic table, including titanium, vanadium, zirconium, niobium, hafnium and tantalum. In some embodiments, suitable valve metals include titanium, zirconium, niobium and tantalum. In some embodiments, the electrode substrate preferably comprises titanium. Titanium may be preferred because of its availability, chemical properties and low cost.

The first coating layer may include a mixture of iridium oxide (IrO ₂ ) and tin oxide (SnO ₂ ). In some embodiments, the first coating layer may consist essentially of a mixture of IrO ₂ and SnO ₂ . In some embodiments, the first coating layer may consist of a mixture of IrO ₂ and SnO ₂ . The iridium oxide in the coating can be in any weight concentration such that the desired properties are achieved, for example passivation or reduction in electrode wear, or increase in the lifetime of the coating layer. The weight concentration of iridium oxide is the weight of iridium oxide compared to the weight of the first coating layer after it has dried (eg, after the solvent has evaporated). In some embodiments, the weight concentration of iridium oxide is in the range of 30% to 85% by weight. In some aspects, the weight concentration of iridium oxide is in the range of 45% to 65% by weight.

The second coating layer may include a mixture of iridium oxide and tantalum oxide (Ta ₂ O ₅ ). In some embodiments, the second coating layer may consist essentially of a mixture of IrO ₂ and Ta ₂ O ₅ . In some embodiments, the second coating layer may consist of iridium oxide IrO ₂ and Ta ₂ O ₅ . The iridium oxide may be in any weight concentration such that the desired properties, such as passivation or reduction of wear of the electrode, are achieved. The weight concentration of iridium oxide is the weight of iridium oxide compared to the weight of the second coating layer after drying. In some embodiments, the weight concentration of iridium oxide is in the range of 40% to 75% by weight. In some aspects, the weight concentration of iridium oxide is about 65% by weight.

The electrode substrate may be applied, for example, with the first and second coating layers according to any application process capable of providing a uniform or substantially uniform dispersion of material on the desired surface. For example, the first and second coating layers may be applied to the electrode substrate by brushing, rolling or spraying, or by atomic or molecular layer deposition or the like. The electrode substrate may be coated with the first and second coating mixtures according to the thermal decomposition method.

The electrode substrate may initially be prepared for application of the coating. For example, the electrode substrate may be treated or cleaned to receive a coating layer or to provide a surface that may allow attachment of the coating layer. Cleaning of the electrode substrate may be performed by chemical degreasing, electrolytic degreasing or treatment with an oxidizing acid. The electrode substrate removes or minimizes contaminants and produces a high surface roughness that can prevent proper adhesion of the coating to the surface of the substrate, lowering the effective current density to the coated metal surface, and also reducing the electrode manipulation potential. It may be prepared by any method suitable for A longer-lived anode translates into less downtime and battery maintenance, thereby reducing operating costs. For example, the electrode substrate may be prepared by cleaning, sand blasting, etching and/or pre-oxidation processes. Other methods of preparing the electrode may include plasma spraying, melt spraying with ceramic oxide particles, melt spraying of the valve metal layer to the electrode substrate, grit blasting by abrupt grit, and annealing. . The cleaning of the electrode substrate may be followed by mechanical roughening to prepare the surface for coating. In some embodiments, when cleaning is performed through sand blasting, this may be followed by an etching process. In some embodiments, the mechanical roughening process may be a frame spray application of a fine particle mixture of metal powder.

In some embodiments, a porous oxide layer may be applied to the electrode substrate to secure the coating layer to the substrate. For example, the electrode substrate may be framed or plasma sprayed onto the electrode substrate prior to application of the electrochemically active material. In some embodiments, the thermally sprayed material may consist of a metal oxide or metal nitride to which the electrocatalytically active particles are pre-applied.

The first and second coating layers may be applied by a thermal decomposition method in a molar ratio suitable to provide desired properties or effects to the resulting electrode. For example, a desired effect or property may be an extended service life by one or both of reduction in wear and avoidance of passivation. In some embodiments, the molar ratio of iridium oxide in the first layer to iridium oxide in the second layer can be from about 1:5 to about 5:1. In some embodiments, the molar ratio of iridium oxide in the first layer to iridium oxide in the second layer can be from about 1:2 to about 2:1. For example, the molar ratio of iridium oxide in the first layer to iridium oxide in the second layer can be about 1:1.

The first coating layer may be dried after application of the first coating layer and before application of the second coating layer. The first coating layer may be air dried and subsequently dried in a first furnace at an elevated temperature and a time sufficient to dry the first coating layer. The furnace may contain a source of oxygen. For example, the source of oxygen may be air. The first coating layer may be dried in a first furnace at a first temperature for a first period of time and subsequently dried in a first or second furnace at a second temperature for a second period of time. One or both of the first temperature and the second temperature may be an elevated temperature. The elevated temperature may be a temperature above ambient temperature. The ambient temperature may be room temperature or the temperature surrounding the object under discussion. Typical ambient temperatures may range from about 20°C to about 25°C; Thus, in certain embodiments, the elevated temperature is at least greater than 20°C. In some embodiments, the first coating layer may be dried in a first furnace at about 80°C to about 120°C. For example, the first coating layer may be dried at about 90° C. in the first furnace. In some embodiments, the first coating layer may be dried in the first furnace for about 5 minutes to about 3 hours. For example, the first coating layer may be dried in the first furnace for about 5 to 60 minutes. In some embodiments, the first coating layer may be dried in the first furnace for about 10 minutes.

Thereafter, the first coating layer may be dried in a second furnace. The second furnace may contain a source of oxygen. For example, the source of oxygen may be air. In some embodiments, the first coating layer may be dried at about 250° C. and about 750° C. in a second furnace. For example, the first coating layer may be dried at about 500° C. in the second furnace. In some embodiments, the first coating layer may be dried in the first furnace for about 5 minutes to about 3 hours. For example, the first coating layer may be dried in the second furnace for about 1 hour. More than one application of the first coating layer may be applied to achieve a desired coating loading.

The second coating layer may be dried in a first furnace at a first temperature for a first period of time and subsequently dried in either the first or second furnace at a second temperature for a second period of time. One or both of the first temperature and the second temperature may be an elevated temperature. In some embodiments, the second coating layer may be dried at about 80° C. to about 120° C. in the first furnace. For example, the second coating layer may be dried at about 90° C. in the first furnace. In some embodiments, the second coating layer may be dried in the first furnace for about 5 minutes to about 3 hours. For example, the second coating layer may be dried in the first furnace for about 5 minutes to about 60 minutes. In some embodiments, the second coating layer may be dried in the first furnace for about 10 minutes.

Thereafter, the second coating layer may be dried in a second furnace. The second furnace may contain a source of oxygen. For example, the source of oxygen may be air. In some embodiments, the second coating layer may be dried at about 250° C. and about 750° C. in a second furnace. For example, the second coating layer may be dried at about 500° C. in a second furnace. In some embodiments, the second coating layer may be dried in the first furnace for about 5 minutes to about 3 hours. For example, the second coating layer may be dried in the second furnace for about 1 hour. More than one application of the second coating layer may be applied to achieve the desired coating loading.

In some embodiments, the coating layer may have a thickness of from about 0.2 g/m 2 to about 3.5 g/m 2 . The thickness of the coating layer may be independent of the dimensions of the electrode.

The electrode may be installed in the electrolyzer. In one embodiment, the electrolyzer also has a power source for supplying current to the electrodes of the electrolyzer. In some embodiments, the source of current may be a direct current source. In the current direction, one electrode typically acts as an anode and its counterpart typically acts as a cathode.

The electrolyzer may be part of the system. For example, an electrolyzer may be used in a wastewater treatment system. In some embodiments, the electrolyzer may be used in municipal or industrial wastewater treatment systems. In some embodiments, the electrolyzer may be used in a chemical processing system. In some embodiments, the electrolyzer may be used in an industrial process water system. For example, an electrolyzer can be used in an electrolytic chlorine production system. The system may include a source of brine. For example, the system may include a source of ballast water. In some embodiments, the system may further comprise a water outlet. For example, the system may include a beverage water outlet. In some embodiments, the system can further include a water storage unit fluidly connected to the water outlet. In some embodiments, the system may further comprise a contaminant outlet. For example, the system may include a chlorine solution outlet. In some embodiments, a system comprising a chlorine solution outlet may comprise a sodium hypochlorite solution outlet. In some embodiments, the system may include a contaminant storage unit fluidly connected to the contaminant outlet.

1A and 1B, a two-coat electrode is provided. The electrode 100 includes a substrate 101 . The substrate 101 may be any substrate having electrically conductive properties. The substrate 101 may be a metal. In some embodiments, the substrate 101 may be a valve metal. For example, the substrate 101 may include titanium, vanadium, zirconium, niobium, hafnium, or tantalum. In some embodiments, the substrate 101 preferably comprises titanium. The substrate 101 may be prepared for application of the coating layer. For example, the substrate 101 may be treated or cleaned to receive a coating layer or to provide a surface that may allow attachment of the coating layer. The cleaning of the substrate 101 may be performed by chemical degreasing, electrolytic degreasing or treatment with an oxidizing acid. The substrate 101 removes or minimizes contaminants, generates a high surface roughness that can prevent proper adhesion of the coating to the surface of the substrate 101, lowers the effective current density to the coated metal surface, and Electrodes can be prepared by any method suitable for reducing the operating potential. For example, the substrate 101 may be prepared by cleaning, sand blasting, etching and/or pre-oxidation processes. Other methods of preparing the substrate 101 may include plasma spraying, melt spraying with ceramic oxide particles, melt spraying of the valve metal layer to the electrode substrate, grit blasting with abrupt grit and annealing. The cleaning of the substrate 101 may be followed by mechanical roughening to prepare the surface for coating. In some embodiments, when cleaning is performed through sand blasting, this may be followed by an etching process. In some embodiments, the mechanical roughening process may be a frame spray application of a fine particle mixture of metal powder.

The substrate 101 may be coated with the first coating layer 102 . The first coating layer 102 may cover at least a portion of the surface of the substrate 101 . The first coating layer 102 may include a mixture of iridium oxide (IrO ₂ ) and tin oxide (SnO ₂ ). The first coating layer 102 may include IrO ₂ in any weight concentration such that desired properties, such as passivation or reduction in electrode wear, are achieved. In some embodiments, the weight concentration of IrO ₂ in the first coating layer 102 is in the range of 30% to 85% by weight. In some aspects, the weight concentration of IrO ₂ in the first coating layer 102 is in the range of 45% to 65% by weight. The first coating layer 102 may be applied to the surface of the substrate 101 by any known application process. For example, the first coating layer 102 may be applied to the surface of the substrate 101 by brushing, rolling, or spraying. The first coating layer 102 may be applied to the surface of the substrate 101 according to a thermal decomposition method.

The first coating layer 102 may be coated by the second coating layer 103 . The second coating layer 103 may cover at least a portion of the first coating layer 102 . The second coating layer 103 may include a mixture of iridium oxide (IrO ₂ ) and tantalum oxide (Ta ₂ O ₅ ). The second coating layer 103 may include IrO ₂ in any weight concentration such that desired properties, such as passivation or reduction in electrode wear, are achieved. In some embodiments, the weight concentration of IrO ₂ in the second coating layer 103 is in the range of 40% to 75% by weight. In some aspects, the weight concentration of IrO ₂ in the second coating layer 103 is about 65% by weight. The second coating layer 103 may be applied to the first coating layer 102 by brushing, rolling, or spraying. The second coating layer 103 may be applied to the first coating layer 102 according to a thermal decomposition method. The first and second coating layers may be applied in a molar ratio of about 1:5 to about 5:1. For example, the first and second coating layers may be applied in a molar ratio of about 1:2 to about 2:1.

Referring now to FIG. 2 , an electrochemical system is provided. System 200 may include an electrolyzer 210 . The electrolyzer 210 may include at least one electrode 100 as described above. The electrode 100 may be at least one of an anode and a cathode. In some embodiments, electrode 100 is an anode. System 200 may further include a power source 230 operatively coupled to electrolyzer 210 . The power source 230 may supply direct current to the electrolyzer 210 .

One or more sensors 240 may be located within the electrolyzer 210 . The sensor 240 may be configured to measure the quality of the system 200 . In some embodiments, the sensor 240 is configured to measure one or more of the pH of the system (eg, the pH of the electrolyte), the temperature of the system (eg, the temperature of the electrolyte), the conductivity of the electrolyte, and the current of the system. can be The sensor 240 may electrically or otherwise communicate with the controller 250 to provide a signal to the controller indicative of a measured characteristic of the system. The controller 250 may control one or more characteristics of the system. For example, the controller 250 may control the number of amperes from the power source 230 to the system.

The functions and advantages of these and other embodiments will be more fully understood from the following non-limiting examples. The examples are intended to be illustrative in nature and should not be construed as limiting the scope of the embodiments described herein.

Example

Example 1:

A first single coating layer electrode was prepared. Electrodes were prepared by coating the surface of a commercial titanium grade 2 substrate with a coating comprising IrO ₂ and SnO ₂ . The titanium substrate was cleaned in a commercially available alkaline bath at a temperature of 60° C. for 20 minutes, followed by cleaning with deionized water. After air drying for about 5 to about 60 minutes, the substrate was sandblasted with aluminum oxide, etched with 10% oxalic acid at 85° C. for about 4 hours, and peroxidized at 550° C. for 2 hours.

Dissolve 4.57 g of hexachloroiridic acid hydrate (H ₂ IrCl ₆ x 4H ₂ O) and 3.58 g of stannous chloride (SnCl ₄ x 5H ₂ O) in 54.8 ml of water while adding 8.7 ml of 2-propanol A mixture of salts of iridium and tin was prepared. This mixture was applied to the cleaned substrate to achieve a loading of 1.5 g/m 2 per coat on a dry basis. The wet coated substrate was allowed to air dry for about 20 minutes and then placed in a furnace where it was heated at a temperature of 90° C. for 10 minutes and at a temperature of 460° C. for 15 minutes. The mixture was re-applied, air dried and heated several times as described above to obtain a total coating loading of at least 5 g/m 2 . An electrode having a first single coating layer comprising IrO ₂ and SnO ₂ was achieved.

Example 2:

A second single coating layer electrode was prepared. Electrodes were prepared by coating the surface of a commercial titanium grade 2 substrate with a coating comprising IrO ₂ and Ta ₂ O ₅ . The titanium substrate was cleaned in a commercially available alkaline bath at a temperature of 60° C. for 20 minutes, followed by cleaning with deionized water. After air drying for about 5 to about 60 minutes, the substrate was sandblasted with aluminum oxide, etched with 10% oxalic acid at 85° C. for about 4 hours, and peroxidized at 550° C. for 2 hours.

The salt of iridium and tantalum was prepared by dissolving 6.47 g of hexachloroiridic acid hydrate (H ₂ IrCl ₆ x 4H ₂ O), 2.86 g of tantalum chloride (TaCl ₅ ) in 61.9 ml of butanol while adding 3.5 ml of concentrated hydrochloric acid. A mixture was prepared. This mixture was applied to cleaned substrates to achieve loadings of 0.5 to 4.0 g/m 2 per coat on a dry basis. The wet coated substrate was allowed to air dry for about 15 minutes and then placed in a furnace where it was heated at a temperature of 151° C. for 20 minutes. The mixture was re-applied, air dried and heated several times as described above to obtain a total coating loading of at least 5 g/m 2 . An electrode having a second single coating layer comprising IrO ₂ and Ta ₂ O ₅ was achieved.

Example 3:

Accelerated anode aging test at a current density of 20 kA/m 2 in an electrochemical cell containing 180 g/l sodium sulfate at a temperature of 60° C. and a pH of 1 for the first and second single coating layer electrodes prepared according to Examples 1 and 2 was evaluated as an anode in The electrolyte was cycled through the cell at 1.5 gph (5.67 lph). The cell voltage was recorded every hour.

The first and second single coating layer electrodes showed different behaviors in the accelerated aging test. The failure mechanisms of the iridium oxide-tin oxide coated electrode and the iridium oxide-tantalum oxide coated anode were different. At the end of the life, as shown in FIG. 3 , the cell voltage rapidly increased at the iridium oxide-tantalum oxide coated electrode, and the cell voltage gradually increased at the iridium oxide-tin oxide coated electrode.

The coating loss at the end of the anode life was then measured. Coating loss was measured as the difference between the original coating loading and the coating loading after anode failure in the accelerated aging test. Coating loading was measured by an X-ray fluorescence (XRF) alloy analyzer. As can be seen in Table 1, the coating loss at electrode failure was about 44% for the iridium oxide-tin oxide coating and about 16% for the iridium oxide-tantalum oxide coating. The amount of coating loss was about 3 times higher in the iridium oxide-tin oxide coating than in the iridium oxide-tantalum oxide coating.

The rapid voltage increase and low mechanical wear rate indicate that the failure mechanism of the iridium oxide-tantalum oxide coated anode is through passivation. The gradual voltage increase and substantial coating loss (approximately 44%) at the iridium oxide-tin oxide coated anode indicates that the anode fails due to mechanical wear and passivation. Based on these results, it can be concluded that the iridium oxide-tin oxide coating is more resistant to passivation and can be used as a protective layer when applied to a substrate. The iridium oxide-tantalum oxide layer with lower mechanical wear rate will act as a second layer protected from passivation by the iridium oxide-tin oxide layer.

Example 4 :

A single coating layer electrode having a titanium substrate was prepared and coated with a layer of iridium oxide-tin oxide coating, a layer of iridium oxide-tantalum oxide coating, or both. The weight concentration of iridium oxide in the iridium oxide-tin oxide coating was 58%, and the weight concentration of iridium oxide in the iridium oxide-tantalum oxide coating was 63%. The coating was applied by a thermal decomposition process from a solution of the corresponding metal salt precursor as described in Examples 1 and 2.

A two-coat electrode comprising both coating layers was prepared. The molar ratios of iridium oxide in the first layer to iridium oxide in the second layer were 1:2, 1:1 and 2:1. The electrodes all had coatings containing 33 g/m 2 of Ir. The electrodes were subjected to an accelerated aging test at a current density of 20 kA/m 2 in an electrochemical cell containing 180 g/l sodium sulfate having a pH of 1 at a temperature of 60°C. The electrolyte was cycled through the cell at 1.5 gph (5.67 lph).

The standardized lifetime of single coating layer electrodes was tested. As shown in Table 2, the iridium oxide-tantalum oxide single-coat electrode has a standardized lifetime (ie, lifetime in virgin coating) of 343 kA*hr/g (Ir), and the iridium oxide-tin oxide single-coat electrode has 454 kA It had a standardized lifetime of *hr/g (Ir). The lifetime of the electrodes was determined by monitoring the electrical resistance of the cells. The current applied to the electrode may be constant, and a rise in voltage may indicate failure of the electrode. In some embodiments, the rise in voltage can be abrupt in that the voltage increases.

The standardized lifetime of the two-coat electrode was also tested. A two-coat electrode with a molar ratio of iridium oxide in the first coating layer to iridium oxide in the second coating layer of 1:2 has a standardized lifetime of 610 kA*hr/g (Ir), which is a single coating of iridium oxide-tantalum oxide 77% increase compared to , and 34% increase compared to a single coating of iridium oxide-tin oxide.

The increase was calculated by the formula ((x-y)/y)*100, where x is the standardized lifetime of the two-coat electrode and y is the standardized lifetime of the single-layer electrode. The two-coat electrode at a molar ratio of iridium oxide in the first layer to iridium oxide in the second layer of 1:1 has a standardized lifetime of 955 kA*hr/g (Ir), which is a single layer of iridium oxide-tantalum oxide. A 178% increase over the coating and a 110% increase over a single coating of the iridium oxide-tin oxide coating. The two-coat electrode at a molar ratio of iridium oxide-tin oxide: iridium oxide-tantalum oxide of 2:1 has a standardized lifetime of 664 kA*hr/g (Ir), which is 93% compared to a single coating of iridium oxide-tantalum oxide. increase and a 46% increase compared to a single coating of iridium oxide-tin oxide.

The results show that two coating layer electrodes with molar ratios of iridium oxide in the first coating layer to iridium oxide in the second coating layer of 1:2, 1:1, and 2:1 were formed of iridium oxide-tin oxide and iridium oxide-tantalum oxide. It shows that the electrode has a higher standardized lifetime than the electrode with the coating. An electrode having a molar ratio of iridium oxide in the first coating layer to iridium oxide in the second coating layer of 1:1 has a higher standardized increase in lifetime compared to both single coatings of iridium-tin oxide and iridium-tantalum oxide. showed A two-coat electrode can exhibit longer lifetime, better performance, less downtime to replace the electrode, and lower cost. Through the use of electrodes with two coatings, a synergistic effect has been achieved. It is believed that a synergistic effect may provide optimal (eg, increased) performance of the electrode as compared to the sum of the performance of the electrode having the first coating and the performance of the electrode having the second coating. In some embodiments, more than two coating layers may be applied to the electrode substrate.

While several exemplary embodiments of the present disclosure have now been described, it should be apparent to those skilled in the art that the foregoing is presented by way of example only, and not limitation. Numerous modifications and other embodiments are considered to be within the scope of those skilled in the art and fall within the scope of the present disclosure. In particular, although many of the embodiments presented herein involve specific combinations of methods, clauses, or system components, it should be understood that these clauses and these components may be combined in other ways to achieve the same purpose.

It should be understood by those skilled in the art that the parameters and configurations described herein are exemplary, and that actual parameters and/or configurations will vary depending on the particular field in which the systems and techniques of the present invention are used. Those skilled in the art should also recognize, or be able to ascertain using no more than routine experimentation, equivalents to the specific embodiments of the present disclosure. Accordingly, it is to be understood that the embodiments described herein are presented by way of example only, and that, within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described.

Moreover, the present disclosure is directed to each feature, system, subsystem or technique described herein, and any combination of two or more features, systems, subsystems or techniques described herein can be It should also be understood that, in the event of inconsistency between , systems, subsystems and techniques, they are considered to be within the scope of the present disclosure as embodied in the claims. Additionally, clauses, components and features described in combination with only one embodiment are not intended to exclude similar roles in other embodiments.

As used herein, the term “plurality” means two or more items or components. The terms “comprising,” “containing,” “having,” “having,” “having,” and “accompanying”, whether in the specification or in the claims, etc., are open-ended terms, i.e., “including, but not limited to. means "not to be". Accordingly, use of these terms is intended to include the items described hereinafter, and equivalents thereof, and additional items. Only the transitional phrases “consisting of” and “consisting essentially of” are closed or semi-closed transitional phrases respectively with respect to the claims. The use of ordinal terms such as "first", "second", "third", etc. in a claim to modify a claim element is itself a claim of any priority, priority or another claim element. It does not imply the order of elements or the chronological order in which the actions of a method are performed, but does not imply a claimed element having a given name, to distinguish the claimed element, having the same name (but for the use of ordinal terminology). ) is used only as a label to distinguish it from another component.

Claims (22)

As an electrode,
an electrically conductive substrate;
a first coating covering at least a portion of the surface of the electrically conductive substrate, comprising 45% to 65% by weight of a mixture of iridium oxide and tin oxide; and
an electrode comprising a second coating covering at least a portion of the first coating comprising a mixture of iridium oxide and tantalum oxide
The electrode of claim 1 , wherein the electrically conductive substrate comprises a valve metal. 3. The electrode of claim 2, wherein the valve metal is selected from the group consisting of titanium, zirconium, niobium and tantalum. 4. The electrode of claim 3, wherein the valve metal is titanium. delete delete The electrode of claim 1 , wherein the second coating comprises from 40% to 75% by weight iridium oxide. 8. The electrode of claim 7, wherein the second coating comprises 65% by weight iridium oxide. delete The electrode of claim 1 , wherein the molar ratio of iridium oxide in the first coating to iridium oxide in the second coating is selected from the group consisting of 1:2, 1:1 and 2:1. 11. The electrode of claim 10, wherein the molar ratio of iridium oxide in the first coating to iridium oxide in the second coating is 1:1. The electrode of claim 11 , wherein the electrode provides a normalized life that is 175% longer than an electrode comprising a single layer coating of the composition of the second coating. The electrode of claim 11 , wherein the electrode provides a standardized lifetime that is 110% longer than an electrode comprising a single layer coating comprised of the composition of the first coating. The electrode of claim 1 , wherein the electrode is an anode. A method of manufacturing an electrode, comprising:
applying a first coating layer comprising 45 wt% to 65 wt% of iridium oxide and tin oxide to at least a portion of the surface of the electrically conductive substrate; and
A method of manufacturing an electrode, comprising the step of applying a second coating layer made of iridium oxide and tantalum oxide to at least a portion of the first coating layer.
16. The method of claim 15, further comprising, prior to applying the first coating layer, electrically preparing the conductive substrate to remove contaminants and develop the surface. The method of claim 15 , further comprising drying the first coating layer after applying the first coating layer. The method of claim 15 , further comprising drying the second coating layer after applying the second coating layer. The method of claim 15 , wherein the molar ratio of iridium oxide in the first coating to iridium oxide in the second coating is from 1:2 to 2:1. A method of making an electrochemical device comprising:
manufacturing an electrode; and
Comprising the step of installing the electrode in the electrolyzer,
The electrode is
an electrically conductive substrate;
a first coating covering at least a portion of the surface of the electrically conductive substrate, comprising 45% to 65% by weight of a mixture of iridium oxide and tin oxide; and
A method of making an electrochemical device comprising a second coating covering at least a portion of said first coating, said second coating comprising a mixture of iridium oxide and tantalum oxide.
A system comprising an electrolyzer, comprising:
electrode; and
a power source for supplying current to the electrode;
The electrode is
an electrically conductive substrate;
a first coating covering at least a portion of the surface of the electrically conductive substrate, comprising 45% to 65% by weight of a mixture of iridium oxide and tin oxide; and
A system comprising an electrolyzer comprising a second coating covering at least a portion of the first coating comprising a mixture of iridium oxide and tantalum oxide.
22. The system of claim 21, wherein the electrode is immersed in an electrolyte.

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